Out of nowhere the other day I pulled into the gas station to get gas, fired the truck up, pulled out in 1st like normal, pulled around to the car wash, threw it in neutral to pay, went to go back in gear and no good, while the truck is running the only gear i could think of shoving into was 3rd. I can grab a gear while its off and once im moving shift with the clutch normally. Clutch engages at the top of the pedal travel not way down on the floor cant get it to slip with foot on the brake and throttle. Replaced the master and slave with a new one piece unit still no good had gears, though tough for about a minute then locked out again. Help?

 

Air pocket maybe? Try bleeding the system again.